Stable isotopic compositions of sulfur in PIRLA sediment cores

1990 ◽  
Vol 4 (1) ◽  
Author(s):  
Brian Fry
Keyword(s):  
Sediment Cores ◽  
Isotopic Compositions ◽  
Stable Isotopic

The chronostratigraphy of Holocene sediments from four Lake Superior sub-basins1Laboratory for Stable Isotope Science (LSIS) Contribution 264.

2011 ◽  
Vol 48 (12) ◽  
pp. 1581-1599 ◽  
Author(s):  
Ayumi Hyodo ◽  
Fred J. Longstaffe
Keyword(s):  
Lake Superior ◽  
Sediment Cores ◽  
Carbonate Content ◽  
Radiocarbon Dates ◽  
Glacial Sediments ◽  
Fine Grained ◽  
Isotopic Compositions ◽  
Stable Isotopic ◽  
Oxygen Isotopic ◽  
Glacial Clays

Radiocarbon dates, rhythmite occurrences, mineralogy, grain size, and stable isotopic compositions of detrital calcite obtained for four sediment cores from Lake Superior have been used to produce a chronology for these fine-grained deposits over the last ∼10 500 cal BP (calibrated years before A.D. 1950). Most of the rhythmites have been interpreted as annual laminations (varves) based on systematic variations in the carbonate content of rhythmite couplets and correlation of the rhythmite packages with varve sequences reported previously for Lake Superior sediments. Glacial sediments in these cores, which consist of red and grey clay, range in age from ∼10 500 to 8800–8700 cal BP. Distinctive carbon and oxygen isotopic compositions of allochthonous calcite in the red versus grey glacial clays point to different sources for this detritus. Final termination of glacial meltwater input into the Lake Superior Basin occurred between 9000 and 8700 cal BP. The significant decrease in sediment carbonate content over this time is a convenient marker for the start of postglacial sedimentation across the Lake Superior Basin.

Stable isotopes in planktonic and benthic foraminifera from Arctic Ocean surface sediments

1988 ◽  
Vol 25 (5) ◽  
pp. 701-709 ◽  
Author(s):  
A. E. Aksu ◽  
G. Vilks
Keyword(s):  
Surface Water ◽  
Arctic Ocean ◽  
Sea Water ◽  
Ocean Surface ◽  
The Arctic ◽  
Size Fractions ◽  
Isotopic Compositions ◽  
Isotopic Analyses ◽  
Stable Isotopic ◽  
Surface Water Salinity

Oxygen and carbon isotopic analyses have been performed on the tests of Planulina wuellerstorfi and three size fractions of sinistral Neogloboquadrina pachyderma recovered from 33 Arctic Ocean surface-sediment samples. Stable isotopic compositions of N. pachyderma are found to be dependent on the test size: larger specimens show considerable enrichment in both δ18O and δ18C. The difference between the isotopic compositions of the 63–125 and 125–250 μm size fractions in N. pachyderma can be explained by biogenic fractionation effects during foraminiferal test growth. Larger (250–500 μm) N. pachyderma displayed accretions of secondary calcite, i.e., the outermost shell contained significant amounts of inorganically precipitated magnesium calcite. Thus, larger foraminifera may not be suited for down-core stable isotopic studies. There is a difference of ~2‰ between δ18O values of surface samples from the eastern and western Arctic Ocean, reflecting large differences between surface-water salinity in these regions. Therefore, oxygen isotopic data may have limited use as a chronostratigraphic tool in down-core studies in the Arctic Ocean, but we can use them to infer past variations in surface-water salinities. Planulina wuellerstorfi also showed depletions of both δ18O and δ18C in its calcite tests relative to calcite precipitated in isotopic equilibrium with ambient sea water; these depletions ranged from −0.8 to −0.9‰ in δ18Oand −1.2 to −0.9‰ in δ18C. This taxon is found to deposit its shell very close to the δ18C of ΣCO2 of bottom waters.

Stable isotopic compositions of hydrothermal vent organisms

1989 ◽  
Vol 102 (2) ◽  
pp. 257-263 ◽  
Author(s):  
C. L. Van Dover ◽  
B. Fry
Keyword(s):  
Hydrothermal Vent ◽  
Isotopic Compositions ◽  
Stable Isotopic

Stable isotopic compositions in precipitation over wet island in Central Asia

2019 ◽  
Vol 573 ◽  
pp. 581-591 ◽  
Author(s):  
Liheng Wang ◽  
Yanhui Dong ◽  
Dongmei Han ◽  
Zhifang Xu
Keyword(s):  
Central Asia ◽  
Isotopic Compositions ◽  
Stable Isotopic
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